The invention relates to electronic equipment comprising a microprocessor, a liquid crystal display screen and a screen driver having a screen memory. The invention likewise relates to a screen driver comprising a memory for storing data to be displayed on a liquid crystal display.
The invention notably has applications to portable electronic equipment, for example, telephones.
Conventional drivers for a liquid crystal display screen, for example, the driver PCF8549 marketed by Philips Semiconductors, notably comprise a screen memory in which a microprocessor of the equipment writes by an external bus the data to be displayed on the screen. The contents of this memory are to be modified by the microprocessor each time one wishes to modify the data to be displayed.
When screen animations are made (modification and/or displacement of data displayed on the screen, progressive replacement of a screen or of part of a screen, rapid display of a succession of images of a series . . . ), the load of the microprocessor thus increases considerably. Furthermore, the number of exchanges on the external bus linking the microprocessor and the screen driver also increases, which brings about an increase of the energy consumed by the equipment.
The problems of power consumption are particularly important in the field of portable electronics, because one always tries to augment the autonomy of pieces of equipment. Moreover, in the case of portable telephone equipment, the microprocessors have a limited power which does not permit them to manage screen animations during communication.
It is an object of the invention to remedy these drawbacks, and notably permit of realization of screen animations at lower cost in terms of load of the microprocessor and power consumption.
Therefore, equipment and a screen driver according to the invention and as described in the opening paragraph are characterized in that said microprocessor has means for transmitting commands to said screen driver, said commands indicating a processing (C1, C2, C3, C4) to be applied to data (L, H) stored in a source location (S) of said memory, and said screen driver has processing means (50) for carrying out said processing.
The actual operations of displacement are realized by the screen driver which sets the microprocessor free from the corresponding load. Moreover, the exchanges of data resulting from the screen animation in essence take place inside the integrated circuit of the screen driver. The capacity of an internal link to an integrated circuit is well below that of an external link between integrated circuits. The consumption caused by the screen animation is thus much lower.
According to the invention only the functions related to screen animation have been transferred to the screen driver. This allows to optimize the size of the screen driver integrated circuit. As the price of an integrated circuit is proportional to its surface, this allows to optimize the production cost of the equipment. This advantage is of particular importance in the area of consumer electronics. Finally, optimization of the surface of the integrated circuit is also essential for product miniaturization.
In an advantageous embodiment, the screen driver has a buffer memory. Such a memory is used, for example, by the microprocessor for storing specific data, for example fonts or icons. The display of these fonts or icons is then directly carried out by the screen driver without the intervention of the microprocessor. Advantageously, these fonts or icons are stored in compressed form in the buffer memory, notably when two grey levels are sufficient for defining them (one level for the background of the screen and one level for the font or icon to be displayed).
In an advantageous embodiment, processing means permit of modifying the data that have been read out before they are copied to the destination memory location. By way of example, these processing means make it possible to carry out video inversions, block filling and decompression of data read from the buffer memory.